Waterproof terminal constructions and electrical heating elements including same



l. JEPSON 3,259,732 WATERPROOF TERMINAL CONSTRUGTIONS AND ELECTRICALJuly 5, 1966 HEATING ELEMENTS INCLUDING SAME 2 Sheets-Sheet 1 Filed001,. 28, 1963 I. JEPSON July 5, 1966 WATERPROOF TERMINAL CONSTRUCTIONSAND ELECTRICAL HEATING ELEMENTS INCLUDING SAME 2 Sheets-Shea 2 FiledOct. 28, 1963 .a-h -'.,1: 1', V

United States PatentO 3,259,732 WATERPROOF TERMINAL CONSTRUCTIONS ANDELECTRICAL HEATING ELEMENTS INCLUDING SAME Ivar .Iepson, Oak Park, Ill.,assignor to Sunbeam Corporation, Chicago, 11]., a corporation ofIllinois Filed Oct. 28, 1963, Ser. No. 319,390 6 Claims. (Cl. 219-436)This invention relates to a waterproof terminal construction which maybe used to terminate electrical heater elements of the sheathed type,and to sheathed electrical heating elements terminated by suchWaterproof terminals. The terminal construction of the present inventionis equally applicable to heat-ing elements which have been cast into thebase of, say, a cooking vessel, and to radiant heating elements such asmay be used in the cover of an electric frying pan.

According to this invention a waterproof terminal construction for asheathed type electrical heating element comprises an annular sealingelement of a heat-resistant flexible material surrounding the centralterminal lead of the heating element and abutting against the end of thesheath, an elongated hollow terminal enclosing the said central terminallead and having an enlarged end between which and the end of the sheaththe sealing element is compressed, an insulator surrounding the lowerend of the terminal and having a well in its base enclosing the enlargedend of the terminal, and a retaining washer surrounding the insulator,the washer being held within a well at the end of the heating elementwhereby the sealing element is held in the compressed state.

Reference will now be made to the accompanying drawings in which:

FIGURE 1 is an underneath view of portion of an electric frying panincluding waterproof terminal eonstructions according to the invention,

FIGURE 2 is a section along the line 2-2 of FIG- URE 1,

FIGURE 3 is a side view of portion of the frying pan including theterminals,

FIGURE 4 is a perspective view of the waterproof terminal constructionbefore assembly,

FIGURE 5 is a side elevation of a modified terminal construction,

FIGURE 6 is an end view of the construction of FIG- URE 5 and FIGURE 7is a section along line 77 of FIGURE 6, but to a larger scale.

The frying pan shown in FIGURES 1 to 3 is of the type having a castaluminum pan 8, the sheathed heating element 9 being cast into the baseof the pan with its two ends 10, 11 brought out in parallel relationshipat one side of the pan, terminals 12, 13 being secured to the ends ofthe heating element whereby an electrical socket can be removablyconnected to the heating element. The base of the pan is thickened atthe terminal end portions to form a heating element terminal supportincluding a cross-shaped casting 14 with its short arm 15 joining thecast-ing portions, which surround the heating element ends and its longarm 16 parallel to the ends of the heating element. A longitudinal hole17 is bored through the long arm of the cross to receive the probe of aprobe type combined thermostatic control and connecting uit. Thisgeneral type of frying pan is Wellknown.

In order that the frying pan may be immersed in water for Washing afterthe thermostatic control and connecting unit has been disconnected, theterminal ends of the heating element must. be made waterproof, and alsothere should be sufficient insulating surface between the exposedterminals and the metallic pan body to prevent tracking. To effect thiseach end 18 of the sheath of the heating element is made to terminate atthe base of an annular well 19 formed in the casting. The well is of astepped construction. The deepest portion of the well, corresponding tothe end of the sheath, has a chamfered edge 20 merging into a largerdiameter shallow well. The edge of this shallow well is also chamferedat 21 and merges into a larger and comparatively deep well 22. At thetop of the well it is enlarged yet again to form a larger diametershallow annulus 23.

The heating element spiral wire ends in a threaded terminal lead 24which extends out of the sheath and the well along their common axis. Asilicone rubber terminal seal 25, which is initially cylindrical asshown in FIGURE 4, is provided having an axial opening which is a tightfit on the terminal lead 24 and an outer diameter which enables thelower end of the terminal seal, when fitted over the terminal lead, to.seat in the lower shallow part of the well 26. A hollow terminal 27 isprovided having an axial bore 28 from its lower end to near its otherend which is a loose fit over the terminal lead. The terminal issuitably shaped over its length, for example it may be cylindrical butpreferably is elliptical in cross-section; its shape is such as to matchthe female connectors in the combined thermostat and connecting unit. Inany case it is formed with a flat circular enlarged base 29 of adiameter slightly greater than that of the cylindrical sealing element25 in its uncompressed state. A ceramic insulator 30 is provided whichis generally cylindrical in shape with an axial opening 31 such that itmay be slipped over the terminal, and has. an upper portion 32 whosediameter or major diameter is less than the diameter of the bottomportion to form a step 33. The underside of the base of the insulator isformed as a shallow Well 34 whose diameter at the closed end is slightlygreater than the diameter of the base of the terminal, and widens towardthe major opening by having a chamfered side wall 35. The largest outerdiameter of the ceramic insulator is such that it seats easily andneatly within the deep portion 22 of the well in the terminal support. Afiat stainless steel ring 36 seats over the external step in the ceramicinsulator and has an outside diameter larger than that of the ceramicinsulator.

To make the waterproof seal the silicone rubber sealing element 25 iscompressed between the enlarged base 29 of the terminal and the bottomof the well by pressure on the terminal, insulator, and ring. Thesilicone rubber expands radially as it is compressed and nearlycomplete- 'ly fills the base of the well in the terminal support and theunderside of the well in the insulator 30 to form the seal. The annularring 36 seats in the uppermost annular step in the well in the terminalsupport the edges of which are then staked over the ring at 37 to secureit in position. Thereafter the terminal 12 is secured to the terminallead 24 to provide a good electrical connection thereto by crimping attwo points 38 on each side of the terminal lead.

In the form of the invention shown in FIGURES 5 to 7 the seal is formedon the end of an exposed type sheathed heating element 39. For examplethe heating element may be one which is secured to the underside of adeep cover for a frying pan, and is used for grilling in the frying pan.In such an application the sheathed heating element is bent into aconvoluted shape and its two ends brought out parallel to each other. Abracket joins the two parallel portions near the ends of the sheath. Thebracket. has two openings through which the sheath ends pass and isbrazed or welded to the sheath at those points. Outward extensions ofthe brackets are bent backwardly parallel to the parallel portions ofthe sheath to provide means by which the heating element is removablysecured to the cover. The portion of the bracket between the sheathportions has a central hole, and two wings which are bent backwardlyabove and below respectively the plane of the sheath portions. Openingsare provided in the wings and a strip spring is secured to one wing,passing through the opening, up to and having a bend received in theopening in the other wing, and back to the other wing. The spring isshaped to receive and make electrical contact with the probe of athermostat connector inserted through the hole in the front face of thebracket.

A well or cup shaped member 40 is brazed or welded to each end of thesheath 41. The internal end 42 of the sheath being chamfered. Theconstruction then is as in the previously described construction, withthe cup-shaped member replacing the case well: the same numerals havebeen used as in FIGURES l to 4 for corresponding elements. Thus thecylindrical silicone rubber sealing element is compressed between theend of the sheath and base of the well on the one hand and the enlargedterminal end and underside of the insulator on the other. The washer 36is held in the cup-shaped member by rolling its edge 43 over the washerand crimping.

What we claim is:

1. A waterproof terminal construction comprising a sheathed typeelectric heating element having an elongated tubular sheath, a centralterminal lead for said heating element, an annular sealing element of aheat-resistant flexible material surrounding the terminal lead andabutting against one end of said sheath, an elongated hollow terminalenclosing the said central terminal lead, an enlarged end to the hollowterminal, an insulator surrounding the inner end of the terminal, a wellin the base of the insulator enclosing the enlarged end of the terminal,means defining a further Well at the end of the heating element sheath,a retaining ring surrounding the insulator and means for securing theretaining ring within the said further well whereby the sealing elementis compressed between said one end of said sheath and the said enlargedend of the terminal and said insulator.

2. A waterproof terminal construction comprising a sheathed typeelectric heating element having an elongated tubular sheath, a centralterminal lead for said heating element, a sealing element of aheat-resistant flexible material which element is cylindrical in itsunstrained state, an axial bore through the sealing element, theterminal lead extending through the axial bore with one face of thesealing element against one end of said sheath, an elongated hollowterminal enclosing the said central terminal lead, an enlarged end tothe hollow terminal abutting the other face of the sealing element, aninsulator surrounding the inner end of the terminal, a well in the baseof the insulator enclosing the enlarged end of the terminal, acircumferentially extending step on the outer surface of the insulator,means defining a further well at the end of the heating element sheath,a retaining washer seated on the step of the insulator, and means forsecuring the retaining washer within the said further well whereby thesealing element is compressed axially between the base of the furtherwell and the said enlarged end of the terminal and insulator and expandsradially to fill the greater part of the base of the well.

3. In a cooking vessel a waterproof terminal construction for a heatingelement comprising a cast metal cooking vessel, a sheathed type heatingelement cast in the cooking vessel, said element including a tubularsheath, means on said vessel defining a well at one end of said sheath,a central terminal lead for the heating element, a sealing element of aheat-resistant flexible material which element is cylindrical in itsunstrained state, an axial bore through the sealing element, theterminal lead extending to the hollow terminal, an insulator surroundingthe inner end of the terminal, a well in the base of the'insulatorenclosing the enlarged end of the terminal, a circumferentiallyextending step on the outer surface of the insulator, a retaining washerseated on the step of the insulator and means for securing the retainingWasher within the well in the casting to compress the sealing elementaxially between the base of the well in the casting and the enlarged endof the terminal, the sealing element expanding radially to fi-ll thegreater part of the base of the well in the casting.

4. A waterproof terminal construction for a heating element comprising asheathed type heating element including an elongated tubular sheath, acup shaped member secured to one end of said sheath, a central terminallead for the heating element, a sealing element of a heat-iresistantflexible material element is cylindrical in its unstrained state, anaxial bore through the sealing element, the terminal lead extendingthrough the. axial bore, an

elongated hollow terminal enclosing the said central terminal lead, anenlarged end to the hollow terminal, an

insulator surrounding the inner end of the terminal, a well in the baseof the insulator enclosing the enlarged end of the terminal, acircumferentially extending step on the outer surface of the insulator,a retaining washer seated on the step of the insulator and means forsecuring the retaining washer within the cup-shaped member to compressthe sealing element axially between the base of the cup-shaped memberand the enlarged end of the terminal, the sealing element expandingradially to fill the greater part of the base of the cup-shaped member.

5. A waterproof terminal construction comprising a sheathed typeelectric heating element having an elongated sheath, means defining awell into which one end of said sheath of the heating element intrudes,a terminal lead for the heating element extending axially of the well, asilicone rubber sealing element which surrounds the inner end of theterminal lead and which is cylindrical in its unstrained state, anelongated hollow terminal enclosing the said central terminal lead, anenlarged end to the hollow terminal, an insulator surrounding the innerend of the terminal, a retaining washer surrounding the insulator, andmeans for securing the retaining washer within the well to compress thesealing element axially between said one end of said sheath and the saidenlarged end of the terminal and said insulator.

6. A waterproof terminal construction comprising a sheathed typeelectric heating element having an elongated tubular sheath, meansdefining a well into which the end of the sheath of the heating elementintrudes, a terminal lead for the heating element extending axially ofthe well, a silicone rubber sealing element which surrounds the innerend of the terminal lead and which is cylindrical in its unstrainedstate, an elongated hollow terminal enclosing the said central terminallead, an enlarged end to the hollow terminal, an insulator surroundingthe inner end of the terminal, a circumferentially extending step on theouter face of the insulator, a retaining washer seated on the step ofthe insulator, and means for securing the retaining washer within thewell to compress the sealing element axially between the base of thewell and the said enlarged end of the terminal.

References Cited by the Examiner UNITED STATES PATENTS 1,177,392 3/1916Dempster 338-238 X 2,372,150 3/1945 Whittaker 338--274 X 2,735,1622/1956 Huck 338-274 X 2,768,267 10/1956 Pass 338274 3,068,342 12 /1962Iepson et al 2l9436 RICHARD M. WOOD, Primary Examiner. ANTHONY BARTIS,Examiner.

3. IN A COOKING VESSEL A WATERPROOF TERMINAL CONSTRUCTION FOR A HEATINGELEMENT COMPRISING A CAST METAL COOKING VESEEL, A SHEATHED TYPE HEATINGELEMENT CAST IN THE COOKING VESSEL, SAID ELEMENT INCLUDING A TUBULARSHEATH, MEANS ON SAID VESSEL DEFINING A WELL AT ONE END OF SAID SHEATH,A CENTRAL TERMINAL LEAD FOR THE HEATING ELEMENT, A SEALING ELEMENT OF AHEAT-RESISTANT FLEXIBLE MATERIAL WHICH ELEMENT IS CYLINDRICAL IN ITSUNSTRAINED STATE, AND AXIAL BORE THROUGH THE SEALING ELEMENT, THETERMINAL LEAD EXTENDING THROUGH THE AXIAL BORE, AN ELONGATED HOLLOWTERMINAL ENCLOSING THE SAID CENTRAL TERMINAL LEAD, AN ENLARGED END TOTHE HOLLOW TERMINAL, AN INSULATOR SURROUNDING THE INNER END OF THETERMINAL, A WELL IN THE BASE OF THE INSULATOR ENCLOSING THE ENLARGED ENDOF THE TERMINAL, A CIRCUMFERENTIALLY EXTENDING STEP ON THE OUTER SURFACEOF THE INSULATOR, A RETAINING WASHER SEATED ON THE STEP OF THE INSULATORAND MEANS FOR SECURING THE RETAINING WASHER WITHIN THE WELL IN THECASTING TO COMPRESS THE SEALING ELEMENT AXIALLY BETWEEN THE BASE OF THEWELL IN THE CASTING AND THE ENLARGED END OF THE TERMINAL, THE SEALINGELEMENT EXPANDING RADIALLY TO FILL THE GREATER PART OF THE BASE OF THEWELL IN THE CASTING.